Graze harvesting of mushrooms involves strategic harvesting of mushrooms from a bed of mushrooms in order to maximize crop yield. Currently, graze harvesting of mushrooms is conducted manually at mushroom farms. Differences in operator training and experience result in variation in harvest results and reduces crop yield. The automated harvesting of mushrooms would provide significant cost reduction to mushroom growers. An important aspect of automating mushroom harvesting is the availability of a gripper that is able to grip the mushroom, remove it from compost, retain it through a stem trim operation and finally deposit it in a packaging tray. The gripper should not cause any immediate or latent damage to the mushroom. In addition, the gripper should be small enough that it does not damage any mushrooms adjacent to the mushroom being harvested. Finally, during graze harvesting for the fresh mushroom market, mushrooms ranging in size from about 15-70 mm cap diameter are harvested. Therefore the gripper should be able to grip a wide range of mushroom sizes.
There have been a few attempts to develop automated mushroom harvesting systems and devices. For example, U.S. Pat. No. 5,058,368 issued Oct. 22, 1991 describes a device for harvesting mushrooms using a suction gripper comprising a bellows-style suction gripper with an internal, porous foam block which is intended to support the mushroom cap. However, the porous foam would quickly fill with mushroom bed compost thereby disrupting the vacuum flow required to pick up the mushrooms. U.S. Pat. No. 5,471,827 issued Dec. 5, 1995 describes a device for harvesting mushrooms using a suction gripper described as a long suction bellows. However, this gripper design would not provide sufficient angular and axial rigidity to make the necessary shifting and rotating movements required to remove a mushroom from a bed. U.S. Pat. No. 8,033,087 issued Oct. 11, 2011 describes the use of commercially available suction pads for gripping mushrooms. However, through testing of a variety of commercially available suction grippers, we have found that they do not work well for harvesting mushrooms, either causing damage to the mushroom caps or being unable to support a reasonable range of cap diameters.
There remains a need for devices and methods for automated harvesting of mushrooms from a mushroom bed, which reduce damage to mushroom caps and/or are able to support a commercially useful range of mushroom cap diameters.